1. Field
Apparatuses consistent with exemplary embodiments relate to wavelength separation devices and 3-dimensional (3D) image acquisition apparatuses including the same, and more particularly, to wavelength separation devices capable of making uniform the light intensity distribution of separated reflected light, and 3D image acquisition apparatuses including the same.
2. Description of the Related Art
Recently, 3-dimensional (3D) content has become more significant along with the development and increasing demand for 3D display apparatuses capable of displaying an image having a sense of depth. Accordingly, research is being conducted into various 3D image acquisition apparatuses, such as 3D cameras, that enable users to personally produce 3D content. The 3D cameras have to be able to obtain depth information together with conventional 2-dimensional (2D) color image information through a single photographing operation.
A binocular stereo vision method using two cameras or a triangulation method using structured light and a camera may be used to obtain depth information about the distances between a 3D camera and the surfaces of an object. However, in these methods, it is difficult to obtain accurate depth information because the accuracy of depth information depends on the surface state of an object and degrades rapidly as the distance to the object increases.
In order to solve this problem, a time-of-flight (TOF) method has been introduced. TOF technology is a method of measuring the flight time of light between when illumination light is direction to an object until the light reflected from the object is received by a light-receiving unit. According to the TOF technology, an illumination optical system, including a light-emitting diode (LED) or a laser diode (LD), is used to project light of a certain wavelength (e.g., 850 nm near-infrared light) onto an object, light of the same wavelength reflected from the object is received by a light-receiving unit, and then a series of processing operations, such as modulation of the received light by a modulator having a known gain waveform, are performed to extract depth information. According to such a series of optical processing operations, various TOF technologies have been introduced.
In general, a 3D camera employing a TOF technology includes an illumination optical system for emitting illumination light of an infrared wavelength band, and an imaging optical system for acquiring an image of an object in order to obtain depth information. The imaging optical system generates a typical color image by sensing a visible light reflected from an object, and simultaneously generates a depth image having only depth information by sensing an illumination light of an infrared wavelength band reflected from the object. To this end, the imaging optical system may include a color image sensor and a separate depth image sensor. In this structure, various methods are proposed to allow a color image and a depth image to have the same viewing angle. For example, a beam splitter may be used to separate a visible light and an illumination light, direct the visible light to the color image sensor, and direct the illumination light to the depth image sensor.